In many community care institutions, for example canteens of large companies or in hospitals, there is a need for food to be distributed seven days a week. If this food is freshly prepared each time seven days a week, high costs are incurred because kitchen staff can only be employed over the weekend if corresponding extra charges are paid. Thus, a method described in the specialist circles as “cook and chill” is used in many cases. In this method the food is only prepared on weekdays with the portions required for the weekend being precooked at this time. After the precooked quantity of food has been prepared, this is chilled to a temperature below 8° C. and stored at a suitable cool temperature. In this case, the temperature should briefly fall below 3° C. at least once. The food mass can then be heated for consumption at the weekend in its entirety or in portions.
A problem with the “cook and chill” method is that hygiene problems can occur as a result of the storage of the food before its heating. In this case, it is not so much the storage at a temperature below 8° C. that is critical since micro-organisms such as bacteria and fungi barely multiply at these temperatures. Rather it is the cooling phase which is to be regarded as the critical stage during which the food passes through a temperature range from 55° C. to the final temperature below 8° C. In this temperature band micro-organisms in the pre-cooked food find optimum conditions for multiplication and thus multiply especially vigorously during the cooling phase.
In order to keep the multiplication of micro-organisms below a tolerable level during the cooling phase, it is necessary for the precooked food to be cooled to the final temperature within the shortest possible time. In order to reliably reduce the multiplication of micro-organisms during the cooling phase, it is essential that not only parts of the food have reached the final temperature within a sufficiently short time but that the food mass from the edge as far as the core has been continuously cooled to the final temperature.
If the food is cooled merely starting from the edge, for example, by placing a container containing the food mass in a refrigerator, the time before the core of the food mass has reached the end temperature depends on the volume of the food mass relative to its edge surface at which cooling can take place. In order to keep the cooling phase during passage through the critical temperature range until the final temperature is reached in the core of the food mass to a tolerable level in the range of less than 120 minutes, especially shorter than 90 minutes, it is thus known that flat containers can be filled with the pre-portioned food and these flat containers can then be cooled individually. However, this pre portioning in smaller containers again incurs higher costs.
DE 40 09 157 C2 describes a method for pre-treating rice wherein the rice is precooked in accordance with a specific temperature process and then dried.
EP 0 338 282 BI discloses a method for sterile precooking of noodle products which can then be packaged ready for consumption after cooking.
DE 37 27 594 A1, DE-OS 1 926 704 and DE 32 00 1.65 A1 each describe agitators wherein the agitator is constructed in the fashion of a heat exchanger and can have a cooling or heating medium flowing through it.